Constitutive c-fos expression in osteoblastic MC3T3-E1 cells stimulates osteoclast maturation and osteoclastic bone resorption

Abstract

The effect of culture supernatants of c‐fos‐transfectcd MC3T3‐El osteob[aslic cells on osteoclastic bone resorption was studied. Human c‐fos cDNA was integrated in the expression vector pH8. and the cells were transfected using the calcium phosphate precipitation technique. Osteoclastic bone resorplion was quantified by the pit formation assay, and the osteoclast maturation from precursor was assessed by the generation of tartrate‐resistant acid phosphatase (TRAP)‐positive multinucleated cells (MNC). The culture supernatants of MC3T3‐E1 transfectants constitulively expressing c‐fos gene enhanced osteoclast‐like MNC formation from haematopoietic blast cells compared with those of control transfectants (P2, was significantly larger than 1646+314 mm² of the control (p<0‐05). The culture supernatants also promoted bone resorption by purified chick osteoclasts (P<005). The results show that constitutive expression of c‐fos gene in osteoblastic MC3T3‐EI cells stimulates osteoclast rnaturation and osteoclastic bone resorption by releasing humoral mediator(s).